Have Oscar Pistorius' carbon-fiber lower legs crossed the line between prosthetics and enhancements? And is it fair for him to compete in the 2012 Olympic Games? Scientists and sports experts alike are being drawn into the debate, as Scientific American's Rose Eveleth explains.

Her piece begins:

Runners who've faced off against Oscar Pistorius say they know when the South African is closing in on them from behind. They hear a distinctive clicking noise growing louder, like a pair of scissors slicing through the air-the sound of Pistorius's Flex-Foot Cheetah prosthetic legs.

It's those long, J-shaped, carbon-fiber lower legs-and the world-class race times that come with them-that have some people asking an unpopular question: Does Pistorius, the man who has overcome so much to be the first double amputee to run at an Olympic level, have an unfair advantage? Scientists are becoming entwined in a debate over whether Pistorius should be allowed to compete in the 2012 London Games.

Pistorius was born without fibulas, one of the two long bones in the lower leg. He was unable to walk as a baby, and at 11 months old both of his legs were amputated below the knee. But the growing child didn't let his disability slow him down. At age 12 he was playing rugby with the other boys, and in 2005, at age 18, he ran the 400-meter race in 47.34 seconds at the South African Championships, sixth best. Now 25, the man nicknamed the "Blade Runner" has qualified for the 2012 Summer Olympics in London, just three weeks before the games were to begin. But should he be allowed to compete?

The question seems preposterous. How could someone without lower legs possibly have an advantage over athletes with natural legs? The debate took a scientific turn in 2007 when a German team reported that Pistorius used 25 percent less energy than natural runners. The conclusion was tied to the unusual prosthetic made by an Icelandic company called Össur. The Flex-Foot Cheetah has become the go-to running prosthetic for Paralympic (and, potentially Olympic) athletes. "When the user is running, the prosthesis's J curve is compressed at impact, storing energy and absorbing high levels of stress that would otherwise be absorbed by a runner's ankle, knee, hip and lower back," explains Hilmar Janusson, executive vice president of research and development at Össur. The Cheetah's carbon-fiber layers then rebound off the ground in response to the runner's strides.

After the German report was released, the International Association of Athletics Federations (IAAF) banned Pistorius from competing. Pistorius hired Jeffrey Kessler, a high-powered lawyer who's represented athletes from the National Basketball Association and National Football League. It soon became clear that the IAAF's study was very poorly designed, so when Pistorius's team asked for a new study they got it. Soon scientists gathered at Rice University to figure out just what was going on with Pistorius's body.